A tire for running on a snowy road surface has been conventionally provided with a plurality of sipes formed at surfaces of land portions of a tread thereof to each extend in the tire width direction so that the sipes cause edge effects to improve on-snow performances such as traction performance and braking performance on a snowy road.
Such a tire as described above having sipes formed in land portions thereof exhibits improved on-snow performances but performances in dry conditions and performances in wet conditions of the tire may deteriorate because the finely-sectioned land portions have poor rigidity. In view of this, there have been proposed three-dimensional sipes in recent years each of which changes configurations not only at a ground contact surface of a tread but also in the depth direction thereof, to facilitate contact between finely-sectioned land portions thereof and thus suppress deformation of the land portions to eventually improve dry performances and wet performances of the tire, as in PTL 1.